andris9/simplesmtp — pull request #50 by mysz (2013-10-24 09:47:49+00:00)
Title: Handling errors which close connection on or before EHLO

Currently client can't handle errors when servers terminate connection on EHLO. Usually this is done with error 421, which tell us:
Service not available, closing transmission channel

So, if server responds with 421 on EHLO (or before EHLO), to not try HELO, because connection is already terminated, but handle error in right way.